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Originally Posted by avro206
not true.
Yes there is a more pronounced 1-2 rpm drop but it won't matter that much because you'll be so far ahead due to the stronger off the line. As for mileage---a 30% drop in rpms will give better mileage period. 1:1 to 0.70.
Lower rpms = better mileage.
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Actually, it is true for many reasons.
1st) Without changing the final gearing, he will get to 35-40mph before the 1-2 shift, and the RPM drop is 47%, which puts a greater load on the engine. Most acceleration advantage is eliminated on the 1-2 shift.
2nd) Again, without changing the gearing, in O/D the RPM might not be high enough for the engine to operate efficiently. Typically, 3.08s came in trucks without O/D and 3.42s for those with. Too much load in O/D can hurt mileage, especially if the tires are tall (like on a truck) and the vehicle is rather heavy (like a truck).
3rd) Without the benefit of the correct PCM controls of the lock-up, the O/D benefits will be negated if/when the converter doesn't unlock when load increases. Especially at lower RPM.
4th) Even with all the best parts, 700R4, 4L60,-E, 4L65E, cannot be built to take the same level of torque as a built 350 or 350C. The reason is the lower first gear reduction.
5th) for the amount of time, agrivation, money, and modifications that must be made for the 700 to operate correctly, it is simply not worth it.
BTW, I am speaking from extensive experience.
For this person, in this case, his money is best spent on the existing TH350C.
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Originally Posted by avro206
Better tell GM to drop the 4 speed autos and go back the dark ages!
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The 700 was born of the low-torque engines of the early 80s, that WAS the dark ages. A time when performance was laughable, mileage was poor, and quality was lousy. It is horribly outdated, and evey though there have been many improvements, it wasn't until the electronic valve body that it became a much more reliable transmission. The PCM control over the operation of the transmission far out weigh the strength and durability of the TH350.